Inverted trailing blade



Feb. 7, 1967 R. P. MAHONEY 3,302,610

INVERTED TRAILING BLADE Filed Oct. 10, 1963 I N VENTOR.

A 'I'TUR EYS United States Patent 0 3,302,610 INVERTED TRATLENG BLADE Ralph P. Mahoney, Beloit, Wis, assignor to Beloit Corporation, Beloit, Wis, a corporation of Wisconsin Filed Oct. 16, 1963, Ser. No. 315,168 8 Claims. (Cl. 118-126) The present invention relates to improvements in mechanism for coating a travelling sheet and more particularly to an apparatus for applying uniform smooth layer coating to a travelling paper web.

The invention pertains to a mechanism which applies a layer of coating to a travelling paper web and removes excess coating and smooths the remaining coating onto the surface of the web with the use of a trailing doctor blade. The invention contemplates providing a rotary backing roll for supporting the travelling paper web, a coating applicator roll forming a coating applying nip with the backing roll beneath the roll, a coating pan having the applicator roll partially submerged therein for carrying coating upwardly onto the surface of the web, a doctor back following said nip having a trailing doctor blade in smoothing relationship with the coating on the uprunning side of the backing roll, and a flexible coating retainer cup-forming extension strip projecting outwardly in advance of the coating blade and forming a coating retaining cup or channel with the blade for containing a quantity of coating against the face of the blade and Web and increasing the hydraulic pressure between the blade and web and improving smoothing operation.

In a coating operation employing a trailing doctor biade it is critical to reduce the imperfections in the coated surface and reduce streaks formed. The streaks are caused by various factors and most streaks originate at the open area next to the heel of the blade. It is also important that to be able to obtain a heavy coating weight and since the excess coating is metered from the surface of the web by the action of the blade higher hydraulic pressures will permit increasing the coating weight.

It is accordingly an important object of the invention to provide an improved coating arrangement utilizing 'a coating applicator means and a trailing metering and smoothing doctor blade wherein streaks formed against the coated surface will be reduced and improved coated paper web will result.

A further object of the invention is to provide a coating mechanism of the type described wherein higher hydraulic pressures between the blade and web are permitted and wherein an additional flushing action at the blade is created with the reduction of open area at the heel of r the blade.

A still further object of the invention is to provide an improved coating mechanism and method for coating a web utilizing an inverted trailing blade wherein a pool of coating is maintained in advance of the blade with excess coating bleeding away at the ends of the blade and/ or over a retaining strip or wall positioned in adv-ance of the blade.

Other objects, advantages and features will become more apparent with the teaching of the principles .of the present invention in connection with the disclosure of the preferred embodiment thereof in the specification, claims and drawings, in which:

FIGURE 1 is a schematic end elevational view of a coating mechanism constructed and operating in accordance with the principles of the present invention;

showing the action of the trailing coating blade; and

'ice

FIGURE 3 is a detailed fragmentary view illustrating a modified form of the invention.

On the drawing:

A horizontal cylindrical rotary backing roll 10 provides a moving support for a travelling paper web W. The backing roll may be driven in rotation by suitable driving means Ida. Coating is applied to the exposed surface of the web W by coating applicator roll 11 positioned below the backing roll 1%). The coating applicator roll 11 may be driven in rotation by suitable driving means 111; at a surface speed equal to that of the backing roll or at a slower speed.

Beneath the applicator roll 11 is a coating pan '12 con taining a pool of coating with the applicator roll partially submerged therein. The applicator roll will carry the coating upwardly on its uprunning surface to form a pool of coating and a coating submerged nip N.

The coated surface of the paper is carried upwardly on the uprunning side of the backing roll 10 and is engaged by a trailing doctor blade 14 mounted on a doctor back 13.

In accordance with the principles of the present inven tion a pool 16 of coating is maintained on the uprunning side of the web on the advance face of the doctor blade 14. For maintaining this pool 16 a flexible strip or cup forming extension 15 is provided. The strip 15 may be formed of a resilient springy material such as is used for shimstock, which is preferably of a weight in the range of 1 to inch thick. This resilient material forms a cup or channel in advance of the mailing blade 14 with the excess coating flowing out over the free edge 20 of the strip and/ or out each end .of the cup or channel 16. The resilient material will deflect away from the backing roll 10 if an excess amount of coating is formed in the channel to prevent undesirable excess coating from being forced past the trailing blade 14.

The strip 15 is formed concave or cup shaped and is preferably secured to the base of the trailing blade to coact therewith in forming the channel. The blade is held between clamping members 17 and 18 with the clamping member 17 forming a supporting holder for the blade and being attached by bolts 19 to the doctor back. Suitable additional bolts such as shown schematically at 18a, hold ing the clamping members 17 and 18. together and clamp the strip 15 against the doctor blade 14.

The coating retaining channel 16 collects coating as it is metered from the travelling web and causes higher hydraulic pressures between the blade 14 and the surface of the travelling web W. This will allow the application of increased coating weight. Also the streaks which may be formed will be reduced because of the additional flushing action at the blade and because of the reduction of the open area next to the heel of the blade where most streaks originate.

At the end of the coating run when the blade and holder are moved away from the backing roll, the coating will drain from the channel 16 and the channel can easily be flushed such as by being hosed out with a stream of water.

In operation the coating will be applied to the travelling web W at the nip N and will be carried up to the doctor blade 14 where excess coating is metered from the web and collects in the channel 16 providing a pool on the advance face of the blade. Coating not used flows out the ends and/ or over the edge 2% of the flexible cup extension or flange 15, and higher hydraulic pressures and improved flushing of the blade improve the coated web.

In other arrangements it is preferred to use a nonresilient rigid member 15, FIGURE 3, ahead of the blade 14 The strip 15' is on the order of /2 to 1 inch thick and is rigidly bolted to the back 13' by bolts 19. The rigid nonyielding strip prevents fluctuations in the coating weight and holds a fixed gap G between the web W on the roll and the stop 15'. The size of the gap G is adjustable by providing a slot for the bolts 19'.

Thus it will be seen that I have provided an improved inverted trailing blade coating mechanism which meets the objectives and advantages above set forth, and which is relatively simple in construction and may be employed upon coaters presently used or in new installations.

The drawings and specification present a detailed disclosure of the preferred embodiments of the invention, and it is to be understood that the invention is not limited to the specific forms disclosed, but covers all modifications, changes and alternative constructions and methods falling within the scope of the principles taught by the invention.

I claim as my invention:

1. A mechanism for coating a travelling paper web comprising,

a rotary backing roll for supporting a travelling web,

a coating applicator roll forming a coating applying nip with the backing roll, a coating pan below said applicator roll so that the applicator roll will carry coating upwardly onto the surface of the web,

a doctor back following said nip having a trailing doctor blade in smoothing relationship with the coating on the web surface,

and a coating retainer member projecting outwardly in advance of the blade and forming a coating retaining channel with the blade for containing a quantity of coating against the face of the blade and web and increasing the hydraulic pressure between the blade and web.

2. A mechanism for coating a travelling paper Web comprising,

a rotary backing roll for supporting a travelling web,

a coating applicator roll beneath the backing roll forming a coating applying nip with the backing roll,

a coating pan beneath the applicator roll with the roll partially submerged therein so that the applicator roll will carry coating upwardly onto the surface of the web,

a doctor back following said nip having a trailing doctor blade on the uprunning side of the backing roll and being in smoothing relationship with the coating on the web surface,

and a coating retainer member projecting outwardly in advance of the blade and forming a coating retaining channel containing a pool of coating against the blade and web and increasing the hydraulic pressure between the blade and web.

3. A mechanism for coating a travelling paper web comprising,

a curved downwardly facing backing surface for supporting a travelling web, means applying coating to the surface of said web,

a doctor blade held against the coated surface of the web following said applying means and located on the uprunning side of the web, and

means retaining a pool of coating against the web in advance of said blade increasing the hydraulic pressures between the blade and web.

4. A mechanism for coating a travelling paper web comprising,

a curved downwardly facing backing surface for supporting a travelling web, means applying coating to the surface of said web,

a doctor blade held against the coated surface of the web following said applying means and located on the uprunning side of the web,

and a coating retaining member projecting forwardly 4 from the blade forming a channel with the blade holding a pool of coating against the blade and web. 5. A mechanism for coating a travelling paper web a doctor blade held against the coated surface of the web following said applying means and located on the uprunning side of the web,

10 and a resilient cup forming extension strip projecting outwardly from the blade ahead of the blade forming a coating retaining cup with the web for increasing hydraulic pressures between the blade and web 15 being sufficiently flexible to yield with excess coating pressure for excess coating to flow over the free edge of the strip.

6. .A mechanism for coating a travelling paper Web comprising,

a rotary horizontal backing roll providing a cylindrical support surface for a travelling web,

a coating applicator roll forming a coating applying nip with the backing roll beneath the backing roll,

a coating pan extending below said applicator roll and having a pool of coating therein partially submerg ing said applicator roll so that the applicator roll will carry coating upwardly onto the surface of the web,

means for driving said rotary backing roll,

means for driving said applicator roll,

a doctor back following said nip,

a doctor blade clamped in said doctor back and held in trailing close-running relationship with the surface of the web for removing excess coating and smoothing coating on the web surface,

and a lightweight resilient strip supported in the doctor back against the blade projecting ahead of the blade and forming a coating retaining cup for the flow of excess coating holding the coating in a pool against the web for increasing hydraulic pressures between the blade and web and improving the smoothing relationship between the blade and coating, said strip having a thickness in the range of /4 to /8 inch.

45 7. mechanism for coating a travelling paper web comprising,

a curved downwardly facing backing surface for supporting a travelling web,

means applying coating to the surface of said web,

a doctor blade held against the coated surface of the web following said applying means and located on the uprunning side of the web,

and a rigid non-yieldable strip positioned in advance of the blade with respect to the direction of web travel defining a gap between the strip and the Web and forming a pool of liquid coating between the blade and the strip for increasing the weight of coating retained on the web surface.

8. A mechanism for coating a travelling paper web comprising,

a curved downwardly facing backing surface for supporting a travelling Web,

means applying a coating to the surface of said web, a doctor blade held against the coated surface of the web following said applying means and located on the uprunning side of the web,

a strip extending along parallel to the blade and posisitioned in advance thereof for retaining a pool of coating in advance of the blade and defining a gap between the strip and web,

and means for adjustably positioning said strip in a fixed position relative to the blade for changing the size of said gap to control the weight of coating applied to the web.

(References on following page) 5 References Cited by the Examiner UNITED STATES PATENTS 2,848,354 8/1958 Daley 117-102 2,995,469 8/1961 Le Claire 117102 3,081,191 3/1963 Smith et a1. 118126 X 6 3,097,107 7/1963 Martinek 117102 3,113,890 12/1963 Johnson et a1. 118126 3,192,895 7/1965 Galer 117102 5 ALFRED L. LEAVITT, Primary Examiner.

E. B. LIPSCOMB III, Assistant Examiner. 

1. A MECHANISM FOR COATING A TRAVELLING PAPER WEB COMPRISING, A ROTARY BACKING ROLL FOR SUPPORTING A TRAVELLING WEB, A COATING APPLICATOR ROLL FORMING A COATING APPLYING NIP WITH THE BACKING ROLL, A COATING PAN BELOW SAID APPLICATOR ROLL SO THAT THE APPLICATOR ROLL WILL CARRY COATING UPWARDLY ONTO THE SURFACE OF THE WEB, A DOCTOR BACK FOLLOWING SAID NIP HAVING A TRAILING DOCTOR BLADE IN SMOOTHING RELATIONSHIP WITH THE COATING ON THE WEB SURFACE, AND A COATING RETAINER MEMBER PROJECTING OUTWARDLY IN ADVANCE OF THE BLADE AND FORMING A COATING RETAINING CHANNEL WITH THE BLADE FOR CONTAINING A QUANTITY OF COATING AGAINST THE FACE OF THE BLADE AND WEB AND INCREASING THE HYDRAULIC PRESSURE BETWEEN THE BLADE AND WEB. 